Substrate bodies coated with hard materials are known in the art. Due to the applied coating of hard materials, optionally applied in several layers, a wear resistant surface can be combined with a tough substrate, capable to sustain high mechanical loads. Basically two processes are used for applying the hard material layer, the Chemical Vapor Deposition (CVD) or the Physical Vapor Deposition (PVD). Such coatings are known easpecially in the field of cutting tools for machining workpieces, where they have the purpose of extending the life of the cutting tool. Usual protective coatings consist for instance of TiC, TiN and/or aluminum oxide. Also multilayer coatings with the layer sequence TiN, Ti(C,N), TiN on a substrate with any desired C:N mixing proportions have been proposed.
For producing wear-resistant layers for machining tools made of rapid machining steel primarily PVD processes are used, while for tools made of hard metals (cemented carbide alloy) CVD processes are preferred. Both processes have advantages and disadvantages. While PVD coatings can be produced starting at approximately 400.degree. C., for the CVD processes far higher temperatures are required, which as a rule lie at about 1000.degree. C. Consequently temperature-sensitive substrates are coated by means of the PVD process, however with this mode of coating it is difficult and costly to achieve a uniform surrounding coating of bodies having a complicated shape.
In "Surface and Coating Technology", 33, (1987) Pages 91 to 103, the properties of ternary nitrides and carbonitrides of the metals titanium, zirconium, hafnium, vanadium, niobium, chrome and aluminum, produced through cathodic sputtering, are tested. In the case of coatings of (Zr,Ti)(C,N), (Zr,Ti)(C,N), (Nb,Ti)(C,N) as well as (Hf,Ti)C and (Hf,Ti)C higher microhardnesses could be reached.
Furthermore from the DE-A1-25 05 009 a process is known for coating inorganic substrates with carbides, nitrides and/or carbonitrides of iron, boron, silicon or the transition metals of the group IVa to VIa of the periodic system of elements through direct thermal reaction of the metals or their derivatives with substances delivering carbon or nitrogen, optionally in the presence of further additives, wherein as carbon and nitrogen donors, among others compounds containing the cyanogen-group with a triple bond between the carbon and the nitrogen should be used. As one of those compounds acetonitrile is mentioned. The coating should be done through the CVD process. The described compounds are exclusively monometallic carbides, nitrides or carbonitrides. It has been found during testing of a process following the teaching contained in this patent that the Zr(C,N) cannot be produced with this process. In all cases the deposition rates per time unit are very low.
More recently the CVD process activated by a corona-discharge plasma (PCVD) has gained importance. With this process it was possible to deposit adherent hard material layers onto tools starting already from approximately 450.degree. C., similarly to the PVD process. Such a process is described for instance in DE 38 41 731 for the deposition of carbides, nitrides or carbonitrides of titanium or zirconium. The individual deposition layers consist of titanium or zirconium nitride, carbide or carbonitride.